The United States Postal Service, along with other private and public postal services, rely heavily on automated scanning, sorting and handling systems to process millions of mail pieces each day. These automated systems necessarily utilize specialized equipment designed to transport, scan, process and sort envelopes and other flat pieces of mail. In many cases, opposed belt and roller type conveyors are used to transport mail pieces along paths including curves, turns and transitions, in some cases conveying the mail pieces through arcuate paths with bends ranging from a few degrees up to 180°. Mail pieces comprising flat, flexible envelopes, postcards, thin brochures and similar items are normally conveyed without difficulty through such paths.
Stiffer and/or thicker mail pieces may, however, present problems when processed with such automated mail handling equipment. Mail pieces that are too stiff and/or too thick may be damaged or destroyed during the sorting process. Such mail pieces may also jam or damage the processing equipment. Likewise, mail pieces that are excessively long and stiff or long and thick can cause similar problems. Consequently, it is desirable to separate mail pieces having physical properties and dimensions that are not compatible with automated sorting and handling equipment at an early stage in the automated sorting process to avoid these problems.
Reisig U.S. Pat. No. 6,032,517 describes an arrangement for measuring the rigidity of flat items with the aid of a conveying path in which the items are transported separately by means of conveying belts, wherein the conveying path has a straight section and a curved section and wherein the conveying belts are made of an elastic material in the region of the curved section. At least one rigidity sensor is provided for measuring the deflection of the conveying belts caused by the item passing through a predetermined position of the curved section, and at least one thickness sensor is provided in the region of the straight section. An evaluation device is provided for determining the rigidity of an item passing through from the values obtained by the thickness and rigidity sensors.
In order to efficiently separate mail pieces having dimensions and physical properties incompatible with automated sorting equipment, it is desirable to consider both the thickness and the stiffness of mail pieces in determining whether a particular mail piece can be processed using a particular application to avoid unnecessary diversion of mail pieces that are suitable for automated processing. For example, a relatively thick, but flexible mail piece may be readily processed through a particular automated sorting line whereas a thin, very rigid mail piece may cause a jam, damage the machinery, or be damaged. In this instance, the thick flexible mail piece would ideally be processed, while the thin rigid mail piece would be diverted. Further, a system capable of sorting a six inch long mail piece with a given thickness and stiffness may jam with a ten inch mail piece having the same thickness and stiffness. Thus, it is desirable to consider length as a parameter when determining whether a particular mail piece can be processed using automated sorting equipment. The present invention addresses these needs.